Liquid crystal display devices are widely used in large display devices such as television sets and small display devices such as mobile phones. Higher value-added devices have been demanded and the development has progressed. In recent years, attention is attracted to the development of low power consumption liquid crystal display devices, in terms of the increase in interest in global environment and improvement in convenience of mobile devices.
Non-Patent Document 1 discloses a structure in which the refresh rate at the time of displaying a moving image and that at the time of displaying a still image are different from each other in order to reduce power consumption of a liquid crystal display device. Moreover, Non-Patent Document 1 discloses a structure in which, in order to prevent flickers from being perceived with change in drain-common voltage due to switching of signals in a break period and a scanning period when a still image is displayed, alternating-current signals with the same phase are applied to a signal line and a common electrode also in a break period so that the drain-common voltage does not change.